Rotor for electric machines.



R. GOLDSGHMIDT. ROTOR FOR ELECTRIC) MACHINES.

APPLICATION FILED JUNE 4, 1912.

Patented Oct. 29, 1912.

finespjf- J EW [ma/en???" UNITED STATES PATENT OFFICE- RUDOLFGOLDSCHMIDT, 0F DARMSTADT, GERMANY.

ROTOR FOR ELECTRIC MACHINES.

To all whom it may concern:

Be it known that I, RUDoLF GOLDSOHMIDT, a citizen of Germany, residingat Darmstadt, Germany, have invented a new and Improved Rotor forElectric Machines, of which the following is a specification.

Electric machines of large diameter usually comprise a magneticallyoperative annular mass that is supported by a radiating central portion,the magnetically operative mass being composed of laminated metal, whileits radiating portion may consist of solid steel, bronze or any othersuitable material.

The annular portion is attached to the radiating central portion bymeans of screws, dovetail joints or the like; the mode of attachmentadopted being designed to prevent the annular portion, whichadvantageously consists of separate segments, from being torn apart fromthe central portion by centrifugal. force. The coefficient of expansionof the material forming the annular portion is, however, almostinvariably different from, and in general, considerably lower than thatof the material of which the radiating central portion is composed; andthis is especially the case when the annular portion consists of verythin sheets of a hard metallic alloy. It consequently follows that inthe construction usually adopted, the strain due to expansion at thecircumference of the annular portion is considerably increased by themore rapid expansion of the radially extending arms of the centralportion. From this it follows that while the strain on the arms is stillinconsiderable, the annular portion may, when its coefficient ofexpansion is low, under certain conditions, be strained even tothebreaking point. The lower therefore the coeflicient of expansion ofthe annular portion or the more defective the connection of thedovetailed joints, the less is that portion of the strain taken up bythe radial arms, and the greater is the chance that the radiatingportion may fail to afford the protection intended, with the result thatthe annular portion may burst before the radial arms are subjected toany considerable strain. The danger of this occurring is increased bythe fact that thematerial of which the annular portion is composed isusually chosen only with reference to its magnetic properties and thatno regard is paid to the question of its strength.

Specification of Letters Patent.

Application filed June 4, 1912.

Patented Oct. 29,1912.

Serial No. 701,662.

Now an object of the present invention is to provide an improvedconstruction of rotor wherein strains in its annular or rim portion dueto its comparatively low'coeflicient of expansion are eliminated ormini-' mized while the strains due to its centrifugal force arepractically borne entirely by the spokes of the central radiatingportion of the rotor. This is effected by subdividing the annularportion into segments which are separately and independently attached tothe ends or otherwise of two arms of the radiating hub portion.

A further object of the invention is to construct the rotor throughoutof uniform strength thus avoiding additions to its mass which merelyserve to increase centrifugal force and hence to limit the maximumrotary speed attainable.

In the accompanying drawings, Figure 1 illustrates in side diagrammaticelevation one construction of rotor according to this invention; Fig. 2is a similar illustration of a modified construction, and Fig. 3 is asection on the line III III of Fig. 1.

In the drawings, 0. indicates the annular and b the radiating portion.The annular portion is sub-divided into separate segments 0 by means ofslots s, which extend throughout the entire width of the segments. Thesetransverse slots or gaps may either be formed in a radial direction(Fig. 1) or they may be stepped by correspondingly stepping the ends ofthe segments as shown at cl (Fig. 2). hen such an arrangement is adoptedthe strains are not borne by the annular portion abut each segment 0thereof transmits its strains to the spokes e of the radiating hubportion 7). Under these circumstances the material of which theradiating portion 1) is composed may be selected solely with referenceto its strength, while it is, moreover, no longer necessary to pay thesame attention to the accurate fitting of the dovetailed joints as inconstructions wherein strains arising in the spokes are transmitted tothe rim. The portion. 6 may advantageously be constructed as of equableor uniform strength throughout, its spokes e tapering outwardly towardthe rim a, as shown in Figs. 1, 2 and 3.

The outer extremities of the spokes 6 may be connected in any suitablemanner with the segments a; in the constructions illustrated theseextremities are enlarged to form dovetailed heads f, engaging withcorresponding recesses in the ends of the ments, the Width of each headbeing greater than the combined depths of a pair of opposed recesses.

hat I claim is:

1. In a ring armature for electric inachines a hub, a plurality ofspokes radiating therefrom, a plurality of segments, each at saidsegments being secured at its ends to the ends of a pair of adjoiningspokes and being separated from the adjacent segments by transverse gapsthat extend outwardly from the spokes, wherebv the strain due toeentritugat action is separately transmitted from each segment to saidadjoining spokes.

2. In a ring armature for electric ma chines, a hub a plurality ofspokes radiating therefrom and having dovetailed heads, a plurality ofsegments having undercut recesses at both ends, the opposed recesses ofeach pair of adjoining segments being engaged by a common spoke-heathwhile the Width of said head exceeds the combined depths of saidrecesses, so as to form a trans Yerse gap between the segments thatextends outwardly from the spoke-head, Wherehy the strain due tocentrifugal action is separately transmitted from each segment to thetwo adjoining spokes.

RUDULF GOLDSCHMIDT. Witnesses ARTHUR E. Zunrn, :KATI-IERYNE K001i.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, D. C.

